With a tablet press, a rotary press is usually meant, with the aid of which not only pharmaceutical pressed articles, but also powder pressed articles for a broad variety of purposes can be produced. Normally, the press unit is located in a casing, which should prevent inevitably generated dust from penetrating into the surrounding room during the pressing process. This is particularly important with a powder material which is toxic in the broadest sense. Due to this, it is known from DE 102 18 220 C2, the entire contents of which is incorporated herein by reference, to seal up the press room sufficiently, so that powder material does not reach the outside In order to improve the sealing action, it is further known to connect a source of negative pressure to the press room, a fan for instance. At the same time, an opening is provided in the press room which permits outer air to flow in. Through this, a negative pressure is constantly generated in the press chamber, on the other hand, dust is sucked off at the same time. A sensor is disposed in the press room for maintaining a minimum negative pressure, the output signal of which is input to a control unit for the negative pressure source, the fan or regulating flaps in the air flow, for instance
With toxic products it is known to convey them all together out of a tablet press into a so-called isolator. In the isolator de-dusting, check of the tablets with respect to its content of active ingredient, hardness and other properties takes place for instance, before the tablets are definitively supplied to a packaging container. For isolators is it is also known to generate a negative pressure in the isolator loom, in order to avoid any escape of dust into the surrounding space.
It is also known to positively pressurize a press room of a tabletting machine, with a protective gas for instance, in order to avoid the entrance of impurities into the press room.
Naturally, breakdown of the control for a fan or even of the fan itself can not be prevented with absolute security. It is known to close the sealed room automatically in such a case, thus “enclosing” the negative pressure. When the sealed room is sealed so effectively that the negative pressure decreases only slowly, persons present in the production room have the possibility to leave it in good time With machines having rotating shafts, a leak-out on the shaft sealings takes typically place, which as well as damages on the sealing elements shortens the duration of the decrease of the negative pressure to a not permissible level.
The present invention is based on the objective to provide a device for generating a negative pressure in a sealed room of a tablet press or of an isolator, by which a negative pressure can be made certain when the negative pressure source breaks down, without having to provide a sealing free or short of leak-out in order to maintain the negative pressure for a longer period of time.